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Do I need to paint a copper plated hull?

I bought a 40' Schooner last spring and after I spend considerable amount of time cleaning the bottom, I was advised by the Marina experts that I would be much better off painting the copper plated bottom for the next season.

I did not like the extra expense, but seeing how much growth there had been on the copper I decided to give it a try. The marina technicians painted the copper with Petit metal primer and then with Interlux Micron Extra. (Since I was at it I thought I better do the best I can) I hoped to have a nice and clean bottom for at least 3 seasons.

Well, I had to haul it out last fall after barely 3 months in Long Island Sound and after a wash to remove the slime it was clean indeed, but half of the primer went away also and continues to peel off in large chunks.

The new season is coming and I wander what should I do... scrape the copper clean again and do the same thing all over just to come back to this same point a year from now...

Has anybody had any experience with copper plated hulls and eventually painting them? I would gladly appreciate some advice.

Copper plating a hull, I assume carvel,
is 3 steps below glassing or coldmolding a carvel hull.
There is absolutely no way to keep water from getting between the copper sheathing and the wood. Any attempt will merely trap moisture between the wood and copper promoting rot.

Copper plating a hull, I assume carvel,
is 3 steps below glassing or coldmolding a carvel hull.
There is absolutely no way to keep water from getting between the copper sheathing and the wood. Any attempt will merely trap moisture between the wood and copper promoting rot.

Hmm, care to elucidate further on this knowledge, first hand or anecdotal?

At your convenience, if you please?

"Lord, grant that I may always desire more than I can accomplish" Michelangelo

RE: Do I need to paint a copper plated hull?

The boat is carvel planked indeed. It is over 50 years old and has been copper plated by a previous owner with a lot of care as much as I can see. BTW I have been told that some old ships have been copper clad as form of antifouling.

Vagabond, that is completely correct. Copper plating is a time-honoured and well proven anti-fouling system. That's what the copper is for. I've never heard of painting such a bottom with anti-fouling paint. It defeats the purpose of the copper. I have no direct experience with it, but my reading indicates that the only maintenance copper needs is a scrub to remove oxidation.

My understanding is we antifoul our bottoms with paint that has COPPER as the antifouling agent (or at least, it used to have). So, I always understood a coppered bottom was a much better way to go, but there are many here with the real answer - i.e. Dave Fleming and many others. I hope they will weigh in.

Copper is indeed a traditional method of antifouling, however, it doesn't work very well as the person who started this thread has already discovered. It is definately worthwhile using antifouling paint as well. The one boat I have seen out of the water used Bottomkote XXX, however, I don't know if a special primer was needed to get the first coat to stick.

If a good job coppering is done, it offers better protection against marine borers such as toredos since if the paint is scratched off, toredos will not attach copper. Because of this you can probably go longer between haul-outs, but there are disadvantages including not being able to inspect the planking to see if one of those sneeky toredos slipped between copper plates and not easily being able to repair or recaulk.

If your hull is in good shape and not leaking I would do a little more research on how to make the paint stick and keep painting it with a compatible antifouling paint (probably a copper based one).

I have never heard of coppering promoting rot and cannot think of any reason that this should be the case unless your boat is stored out of the water in the rain (which isn't a good idea anyway).

P.S. Most propellors are made of bronze or brass which are alloys that have a large amount of copper in them. Anyone ever have anything grow on their props? I believe there is more than just elemental copper in antifouling paint.

There was a story in WB mag many years ago about copper cladding. As I recall anti-fouling paint is still required but it does provide superior protection. The bottom must be tarred before the copper is tacked on.

The reason someone would suggest painting over copper is that copper plating eventualy leaches to a passive state where all the exposed and fixed biocidic copper ions are oxidized. The only way to "re-activate" the plating is to abrade it to expose "new", unoxidized, copper.

Modern copper bottom paints are made to slowly leach copper ions to the surface so as to keep the biocidic properties of the coating up.

Old copper bottoms were applied over tar or tared felt (irish felt) with copper nails. This was to seperate the copper from the bronze or iron plank fastenings to try to prevent electrolosis. Before that hulls were tared to attempt to make them unpalateable to worms. So every year the hull was carrened, burnt, scraped, and re-tared.

Last edited by John E Hardiman; 03-17-2007 at 12:43 AM.
Reason: spelling

First: congratulations. You certainely have got a nice boat...and some pics would be appreciated.

Concerning your question:

It is a fact that copper is not as performing than antifouling paint for keeping the weed/ barnacles away and will required you to scrub her bottom more often.. Some people then advocate (quite abruptly sometimes like pcford hereabove) to paint copper shieved hulls (not sure about the spelling...but the word I ve been taught is the correct one sounds like that...? ). Most of those I ve met who did it have regretted it. Some because the paint had some bad chemical reaction with the copper, and damaged it, some because they, finally, found that the expense of hauling out for a couple of days, painting, was not worth it compared with scraping underwater or being in the slings of the travel lift for 1/2 an hour. All were feeling that they had damaged a nice work. May I add that - excuse me Jimmy and J. Hardimann- but ,although your remarks are founded, painting with copper based paint is to me a bit of a nonsense. If painting: use at least a poinsonous one - still NOT with heavy metals (see above remark).

Then, and in relation with the above remark: it is your choice if you want to disolve in the sea some arsenic and other poisons, or use an obviously not damageable metal (if it lasts so long means that it is not disolving much poison - hence its relative lack of efficiency ).

Concerning wood borers: it is undeniably top! If there is some damage, by a scratch or some oxydation (sometimes concentrated around a certain nail (???), it is a possible entry for the worms. Injection of some poison (xylophenol) when the boat is hauled out and a repair patch. Repair underwater is easy too.

Then is the question of wood condition below the copper. Not much worry there: copper is one of woods best friend: heard about cuprinol? If planking rots, it will more likely be inside than outside.

Hereafter is a couple of pictures showing a nearly 80 years old copper bottom. Some plates had been renewed because of some damage, and of course the waterline ones (between wind and water) a few times. I could tell by the fact that some had been nailed into the wood once only. By the way, it is a good thing to have one strip of copper plates, nailed above the lower ones, and that runs at the waterline, just for the ease of renewing them.

Renewing copper plates is no cheap thing then. One has to buy electrical copper (99.9% pure), plus the nails...plus a considerable amount of time. The copper plates that were renewed on that boat were because the floors and many frames had to be replaced (and their thru-hull fastenings removed), as well as the dead wood aft, which had effectively been attacked by worms where the copper was damaged (when touching the bottom), and replaced by a (heavy!) piece of greenheart...kind of hard to chew on, even for toredoes. Otherwise, judge by yourself of the condition of the old plating, including the one on the rudder.

...and you will see that she still shows her bottom with......PRIDE !!!

Amazing... truly amazing... The one eyed man is king in the land of the blind, I'd guess.

PC's given the only straight-on correct answer. Some of the rest are truly out there!

Copper sheathing properly applied protects against marine borers because they dull their teeth on it. It provides a mechanical barrier.

Algae and other marine flora will eventually grow on just about anything short of bottom paint containing specific biocides, some of which contain copper compounds. If you want to keep the weeds off, you have to use bottom paint.

If your bottom paint is coming off in sheets, there is something wrong with the way it way applied or the product was not compatible with the copper surface. I've never seen anything other than ordinary ablative bottom paint on copper bottoms and I've never seen any peeling problems. The new fangled poly-whozitz stuff is tricky to use. You should be expecting the yard to do the job over and do it right.

Amazing... truly amazing... The one eyed man is king in the land of the blind, I'd guess.

PC's given the only straight-on correct answer. Some of the rest are truly out there!

That is your opinion.....

Some advocate antifouling, some dont. I dont, but to be precise, that is considering that most people use their boat during their summer holidays only, where a good scrubbing and a month sailing after that will not show hardly any growth on the hull (you could not scrub a one year old antifouling without having to give it an other coat). The rest of the year the hull will be very well protected behind its copper. Only if someone uses his boat all year round could antifouling be reasonably considered.

P.S. Most propellors are made of bronze or brass which are alloys that have a large amount of copper in them. Anyone ever have anything grow on their props? I believe there is more than just elemental copper in antifouling paint.[/QUOTE]

I have... just spent the better part of a day last week cleaning up two 23" bronze props that spent one season in salt water...

Amazing... truly amazing... The one eyed man is king in the land of the blind, I'd guess.

PC's given the only straight-on correct answer. Some of the rest are truly out there!

Copper sheathing properly applied protects against marine borers because they dull their teeth on it. It provides a mechanical barrier...

Out there indeed Bob! The idea that teredos chew on the copper until their teeth are dull trying to get at a boat is really silly. Teredos won't attack anything that isn't exposed wood. On top of that, they don't even use their radula (the closest thing a molusc has to teeth, if this molusc even has one at all) to bore into wood. They bore into wood with the other end of their body and there is debate among biologists whether they actually grind away the wood with their shell or use their foot and/or some kind of chemical reaction (nobody has actually watched them at it since it is ... boring). At the stage when teredo larvae attack wood they are microscopic in size and can easily get through any small hole or gap between plates and so the layer underneath the copper is just as important as the copper itself.

The bottom line is that stuff will grow on copper and to keep it clean you either have to scrape/scrub it regularily or paint it with antifouling paint. I think what the person who started this thread needs to know is what paint is best for his boat if he decides to go that route and how to make it stick.

I've also scrubbed the bottom of my boat in scuba gear and plan to do it again. It's hard work, but it's a practical solution for some people (obviously not everyone). For others there is hauling, careening, and antifouling paint.

Thanks for the biology lesson on terredos. I suppose I shouldn't have taken such liberties with the language. It would have been more accurrate indeed to simply say that the copper keeps the buggers from getting to the wood.

That said, it bears noting that different conditions will result in different rates of fouling. Different locations, temperatures, levels of salinity and polution will result in different types of flora and fauna. You have to tailor your antifouling program to the waters in which you plan to sail and even how often and fast you sail. All of that affects what grows on your bottom.

I went diving last week ...

Originally Posted by Gary E
Just who has the time, the diving tanks, and the wet suit to scrub the bottom of a 40 ft boat in 50 deg water???
Anyone who sugests it just aint ever done it, let alone dunit well.

Cleaned the bottom, did a good job.
LOD: 39'8"
Water temp: 52degF

I don't mean to imply it was easy. Diving in cold water all rubbered up is non-trivial. I felt vulnerable to little screw ups that in warmer water and a less bulky suit would be no problem. I had a 5 gal jug of warm water to prewarm the suit and to warm me up about 30 minutes into it.

Dave
Actually I think it's pretty much common sense.
Sheath a wooden hull with copper below the waterline.
The very best seal you can hope for is some sort of goop.
The copper is nailed on, I guess you could try and seal every nail with more goop.
Now we put the boat in the water for however long before haul outs.
The bottom is out of sight out of mind.
When we do haul out all we have to do is clean the copper.
Now if we have any incidental leaks between copper and goop we have no clue until the leak becomes bad enough that it gets through the caulking at which point the fastenings and wood have been exposed to water for....say ...4 years.

IMOOP, a properly done coppering job, one with a freshly corked and payed hull with Irish Felt set in bear ****e over the payed hull and then the copper plating added is not such a bad idea.

As I understand it, coppering a hull is principally for toredo protection not so much for anti-fouling.

Down here in 'insane Diego', the waters rarely exceed 68 degrees in the late summer months. They range in the mid to high 50's in the colder winter months.

There are a number of people who do nothing but scrub bottoms year round.

A 'shave 'n haircut' are just too expensive for most in the water boat owners.

It is not unusual to see at least 8 or so small pick'em'ups with air tanks and coils of hose in the bed whilst the driver is dressed in his wet suit with top pulled down and a sweat shirt on travelling from marina to marina and even into the 'hallowed grounds of the San Diego Yachit Club.

YES, there is that possibility that something will puncture the copper but, for me if it came down to keeping those little ( not so little after they have fed on your planking ) by coppering a wood hull I would not hesitate to do it or have it done.

Problem out here is that there is a dearth of shipwrights with ANY wood hull experience not to mention coppering a hull.

So a person buys whatever bottom paint is working for the area, has the boat scrubbed in the water on a regular basis and hauls out, mortgaging his first born son, each year or so to have the bottom paint renewed-touched up.

But,making the statement that, it is akin to encapsulating a wood hull in feeberglas is to me, a bit much.

If ya get my drift?

"Lord, grant that I may always desire more than I can accomplish" Michelangelo

Paul Revere's copper bottom on the USS Constitution

"But the Constitution was too slow to sail in company with the President. She was moving through the water like a barge, and Captain Hull knew why. Seven years had passed since her bottom had been sheathed in Paul Revere's copper, and she was due for a thorough cleaning. On July 26 [1810], in Hampton Roads, Hull arranged to have divers examine the frigate's bottom. They found enormous colonies of barnacles, mussels, oysters, and seaweed. * * * The Constitution, Hull told secretary [of the Navy Paul] Hamilton, had 'ten waggon loads of them on her bottom . . . you can have no doubts as to the cause of her not sailing.'

"In August, Hull took the Constitution up the Delaware river into fresh water hoping that the saltwater shellfish hanging from the hull like 'bunches of grapes' would perish and fall off. The mussels let go quickly, but the oysters were more stubborn. Two weeks of vigorous scouring with a custom-designed iron scraper were needed to restore the ship to a respectable condition."

Six Frigates, Ian W. Toll, p. 319.

A compelling account of the early navy and the War of 1812 -- highly recommended.

Actually I think it's worse than glassing a hull. At least with glassing you can seal the joint.
Let's step back and consider the options. Glassing may add too much stiffness to the hull, so lets try dynel or xenol, more flexible yet still sealed.
I don't care what anyone says, you cannot seal a copper sheathed bottom.
I't's been done for hundreds of years but those boats are the ones that come up for toatal restorations costing twice the cost of replacement.

I've mused about coppering bottoms for a long time. I've examined several of them. Hal Sommers spent a lot of time, effort and money coppering Wanderbird when restoring that large schooner. I think in that instance it was a good idea, given her size and the cost of hauling her. On the other hand, while the copper does provide a mechanical barrier for borers, if applied properly, I've come to think that today's bottom paints are a better alternative. They are lighter in weight, easier to apply, far less expensive, and, again if properly applied, every bit as effective. Copper was a sound alternative before biocidal bottom paints were perfected. Now, if we could only convince the eco-nazis that bottom paint is SUPPOSED to kill marine growth, we could go back to using the good stuff!

Another thing to be considered is that the copper needs to be renewed...It does not last forever.

I looked at a boat with a copper bottom with a client. The current owners paint the bottom, haul every couple years and scrub the bottom by a diver between haul-outs. Replacing copper was an expected part of maintenance.

One gets the sense that some people think that copper is a one time only answer for bottom maintenance. The answer is that the bottom still needs to be painted with antifouling and the copper has some kind of finite life span, though I have no idea how long this might be.

With the current horrifying cost of copper and its alloys, a copper bottom is a proposition to carefully consider.

Chan: you have no expertise (or even the smallest knowledge)
on the subject, you have not even understood what it is all about, so you better step out.

Greg: please do not give as a significant example a boat whose bottom has not been cleaned for seven years. Of course Capt. Hull knew why she was moving like a barge!!!

Bob Cleek: Nice to read your now semi-moderated posts, although this eco-nazi statement is a bit overdone. Trouble is that, in your urge to show yourself, you have not taken the care of reading the original question, which is not about the cost or usefulness of copper-cladding a bottom, but about antifouling it. If you want to give a useful information based or your real experience/ knowledge to who asked for it, just answer the question.

Pc ford: what you say about a copper clad bottom damaged after having been painted is very right. It most often has desastrous effects on the copper. Not painted, however, it will surely not last forever, but quite some time . Anyway (again) please consider (like B.Cleek hereabove) that the boat is already copper clad. Then, if you also have any useful informations about the methods to antifoul - or not - not the *philosophy* of copper cladding - I think that it would interesting to know about them.

Vagabond: read Dave Fleming posts: he DOES know what he is talking about. And also do I, some like it or not.

Thank you all for the advice.. I am verry happy that this question sparked a nice discussion. I certainly learned a thing or two already.

From the limited information I got while purchasing and fixing the boat it seems that my copper sheets were nailed on top of a thick tar layer with a lot of care. So far so good, but that was some 20 -30 years ago. The copper still seems in decent shape for the age and I have not noticed any structural issues with the hull. ( I have some unpleasant leak at the stern. Water flows up from around the sides of the keel support and from there flows down into the bilge, but that is a whole other issue.)

Back to the antifouling, I believe the primer did not stick because the marina experts painted it directly over the copper and it had formed patina from the atmosphere exposure. Not to mention that it took me about 5 week-ends to clean it with a wire brush.

Having in mind, how much labour it is to clean it again, I am inclined to just paint a new ablative on the bare copper and remnants of primer. I wander if that would stick to the copper at all though. Any Ideas?

Of course the proper way would be to remove the primer leftovers shine the copper and try to put new primer while working in segments not to allow for any (visible) oxidation to occur on the surface of the copper before priming, but ... I'd rather deal with the leak first and save some time for boating.

Oh...I dunno.....I've been on a couple of cupro nickle boats and they did welll..........considered it myself.......it would have cost a couple of sons and at least three daughters and I was one short.....

Wakan Tanka Kici Un
..a bad day sailing is a heckuva lot better than the best day at work.....
Fighting Illegal immigration since 1492....
Live your life so that whenever you lose, you're ahead."
"If you live life right, death is a joke as far as fear is concerned."

Back to the antifouling, I believe the primer did not stick because the marina experts painted it directly over the copper and it had formed patina from the atmosphere exposure. Not to mention that it took me about 5 week-ends to clean it with a wire brush.

Having in mind, how much labour it is to clean it again, I am inclined to just paint a new ablative on the bare copper and remnants of primer. I wander if that would stick to the copper at all though. Any Ideas?

Of course the proper way would be to remove the primer leftovers shine the copper and try to put new primer while working in segments not to allow for any (visible) oxidation to occur on the surface of the copper before priming, but ... I'd rather deal with the leak first and save some time for boating.

I would clean to good adheasion, and use a self-etching metal primer (such as Pettit 6455) before painting with an anti-fouling. Also, copper on wood is given to movement so I would not use a "hard" bottom paint, which may be why it just sheeted off.

LL -- slow down and read in context.

Lucky Luke --

You are too quick to take offense. At least three previous posters had assumed that a copper bottom was a "well proven anti-fouling system" standing alone. I posted as "a significant example" the case of a well-know ship for which copper was not an effective, long-term anti-foul system by itself, and that cleaning of the copper bottom seemed necessary and desirable. I said nothing about paint. How is this hsitorical example at odds with what seems to be your opinion?

The ablative I used was Interlux Micron Extra, it worked for the barnacles, but it seems to be wearing off pretty quick. (for its price at least) I wander also if it would stick well to the copper. Any suggestions?

Some of you guys seem to think that calling something an "anti-fouling system" (as I did) means that it will never ever allow anything to grow on it. C'mon guys - every system known to mankind needs periodic maintenance, including anti fouling, and including copper. Some very experienced sailors - Hiscock, Pye, Tangvaald and plenty of others, have sailed thousands of miles in copper bottom boats with no paint and reported very good results. The truth is that all other things being equal, the more a boat moves, the less stuff grows on it. Nothing I know of will keep a stationary boat slime or growth free - not paint nor copper nor anything else. That story about the Constitution leaves out an important point - it was normal practice to bream copper-clad vessels more often than every 7 years. In the Royal Navy of the period, every 2 years was normal practice. Everyone knew then that excess growth was a result of poor maintenance, and not because she was coppered. I've spend a lot of time musing about this as well, and a lot of time in serious research on the right way to go about it. Copper IS a proven anti-fouling system - meaning if it's properly maintained, it'll keep the critters and the slime to a minimum. As several posters have said, maintenance is a matter of scrubbing or abrading to remove oxidization, which is a job about the same order of magnitude as removing old paint and putting on new.

Vagabond, you didn't say whether you'll sail the boat a little or a lot. If it's a little, maybe your local experts are right, and the good advice you got here about what to use under the paint will be useful. If you plan to sail her a lot, then traditional views support the idea of no paint, despite what many have said here. In the end, it's your bottom, and if you read the books of the guys who sailed many many years with copper bottoms, the answer is pretty clear.

The myth of anti-fouling paints: your bottom will foul anyway, only at a slower rate than an unprotected hull.

The chief ingredient of anti-fouling paints is copper salts. Marine organisms are detered, not totally prevented, from attaching to the hull so painted. Copper plating works the same way, but lasts longer and adds some additional benefits. Copper salts also inhibit the grow of wood rotting fungi in the wood, and thus extends the life of the wood.

Before placing the copperplate, shipwrights would nail a layer of felt onto the hull, with copper nails...a lot of them. Then they would coat the felt with pitch and then attach the copper plate...again using copper nails. The copper nails would slowly disolve and soak the felt layer with copper salts. Thus it was the felt layer that was the best protection from worms and other organisms, and the copperplate protected this softer layer as well as reinforcing thel copper salt effect on the hull.

Back 100 years ago, when double-planking a hull (not an uncommon occurance), the shipwrights would drive copper nails into the surface of the first layer of planking before beginning the outer layer. The purpose is that the copper nails would slowly disolve into copper salts and permeat the wood and inhibit rot from forming between the plank layers.

In many cases (considered a traditional and effective method to this day), muslim cloth was nailed (using copper nails) to the first plank layer, soaked with linseed oil, and then the outer planking was done.

Monel or Cupro Nickel's, copper content according to my
Machinery's Handbook and McGraw-Hill's Machining and Metalworking Handbook varies in content from 65 to 67 % Nickel and 29 to 30 % Copper with various other minerals as dictated by the intended use.

There are literally a 'gazillion' possible Nickel-copper alloys!

CORRECTION or UPDATE:

The edition of Machinery's Handbook I quoted from is the 13th Edition, published in 1946. After reading the web site Gary E. cited I stand corrected regarding the alloy content particulars.

Mea Culpia.

Last edited by Dave Fleming; 03-20-2007 at 03:30 PM.

"Lord, grant that I may always desire more than I can accomplish" Michelangelo

Mate, 5 weekends with a wire brush to clean a 40' hull does sound like doing it the hard way. A tool like a paint scraper might be better-but will it catch under the heads of all the copper nails holding the copper sheathing in place? Or a high pressure water blaster-but again you'd need to be careful to check that it doesn't actually lift the copper sheets off. Maybe the difficulty of scrubbing growth off is a real issue with a copper sheathed hull? Sorry I can't add anything to answer your actual question, just thought I'd weigh in with some more inivited tangential musing.

While an effective barrier against marine borers, copper sheathing should be bedded on tar and Irish felt. Copper sheathing will not prevent growth from forming on it's surface and must be periodicly scrubbed. The most effective treatment I have ever found is, to prime a new hull with creosote prior to applying bottom paint. Mix creosote with the first two coats of bottom paint. Add red pepper to the last coat. It is not as toxic to the environment as you might think. Just don't drink it or get it on your skin. The amount of toxins emitted by pleasure boats is so small as to not even be accountable when compared to sewage out falls, oil tankers, river and land run off, jet fuel, automobile exhaust and tire residue to name a few.
JG

Now...Jay...you are perpetuating a myth....I have been told so by many "experts" on this forum...I mentioned the use of the red pepper and got an earful........

Wakan Tanka Kici Un
..a bad day sailing is a heckuva lot better than the best day at work.....
Fighting Illegal immigration since 1492....
Live your life so that whenever you lose, you're ahead."
"If you live life right, death is a joke as far as fear is concerned."

Before placing the copperplate, shipwrights would nail a layer of felt onto the hull, with copper nails...a lot of them. Then they would coat the felt with pitch and then attach the copper plate...again using copper nails. The copper nails would slowly disolve and soak the felt layer with copper salts. Thus it was the felt layer that was the best protection from worms and other organisms, and the copperplate protected this softer layer as well as reinforcing thel copper salt effect on the hull.

Now...Jay...you are perpetuating a myth....I have been told so by many "experts" on this forum...I mentioned the use of the red pepper and got an earful........

Well, I don't know about the myth part of it, Walt Pikula, former skipper of Black Finn, spent time in the Caribbean where the locals swear by it. I thought it was a lot of bull, but tried it any way and found out that it works! I think the chemical contained in red pepper is called "Capsicum" it is of the "Night Shade" family.
Jay